To my knowledge, the material specs for the cage have been the same for the last 10-15 years at least.

To say they need heavier gauge cage material is to say that the cages are failing. To my knowledge, none of the cages have failed. There are some that have been bent, but no complete failures.

Every crash has to be judged on it's own as all are different, but of the crashes I have seen on the local scene, the cages have held up well. I can't speak of any of the ones that I haven't seen.

I personally haven't seen any thing that would want me to change the current material specs or the Halo area. I do like the extentended style of cage design though.

You can also look at it this way as well. If the cage is too rigid and hits the fence first, then instead of it deforming and absorbing the energy, the driver moves and stretches as the energy is transfered. There is a fine line and I believe that the specs and manufactureres are doing a good job of walking that line right now.

The reason containment type seats are required or at least heavily suggested as they are designed to act as a sort of cocoon for the driver and while they don't or can't prevent all injuries, they do act as another safety defense against certain types of impact.